Psychoanalytic theory can be said to have evolved through several formative eras, each characterized by a conceptual emphasis on a particular aspect of human psychic development and functioning. The first era of initial discovery, termed the era of id psychology, was concerned mainly with libido theory and the role of the sexual and aggressive instinctual drives in the clinical phenomena of conflict, anxiety, repression, unconscious conflict, and symptom formation. The main yield for developmental theory was Freud's (1905) formulation of the oral, anal, phallic-oedipal, latency, and adolescent stages of psychosexual development. In this formulation, the focus is on infant sexuality, less so on aggression. What is articulated is the child's progression through these successive stages, each with a characteristic